Method for producing epoxidated glyceride acetates

ABSTRACT

Epoxidized glyceride acetates are made by a process which comprises reacting an epoxy fatty acid ester and triacetin.

This invention relates to a process for the production of epoxidizedglyceride acetates in which epoxy fatty acid esters are transesterifiedwith triacetin.

In the processing, more especially the molding, of halogen-containingorganic plastics, more particularly polyvinyl chloride (PVC), additivesare generally incorporated in the plastics with the intention ofperforming certain functions. The additives may be required to developtheir effect during processing itself or to impart certain properties tothe moldings or workpieces thus obtained.

An important class of such additives which are widely used are theso-called plasticizers. As well-known to the expert, the plasticizermarket has long been dominated by so-called phthalates or adipates.Dioctyl phthalate (DOP) and dioctyl adipate (DOA) in particular areroutinely used as plasticizers.

However, there has long been a need to replace the traditionalplasticizers mentioned, such as DOP or DOA, by plasticizers with adifferent structure. A technical solution to this problem was proposedin U.S. Pat. No. 2,895,966 published in 1959. This document proposesepoxidized monoglyceride diacetates, for example monoepoxystearyldiacetoglyceride, as plasticizers for plastics and states that, besidescertain stabilizing properties, compounds such as these in particularhave a plasticizing effect and, in addition, may readily be incorporatedin numerous plastics, i.e. are compatible with those plastics.

According to U.S. Pat. No. 2,895,966, the plasticizers are produced byinitially preparing monoglyceride diacetates based on unsaturated fattyacids and then subjected them to epoxidation. However, the plasticizersproposed in U.S. Pat. No. 2,895,966 were never successfully used inpractice. A major reason for this may lie in the fact that they aredifficult to produce on an industrial scale. According to the technicalteaching disclosed in U.S. Pat. No. 2,895,966, an oil having acorresponding content of C═C double bonds in the fatty acid units isfirst subjected to transesterification with glycerol, followed byacetylation and finally—in a third step—by epoxidation. After eachprocess step, the crude product obtained is elaborately purified. Moreparticularly, the crude product obtained after the transesterificationwith glycerol is washed with water to remove any soap formed andglycerol. The crude product obtained after acetylation with excessacetanhydride is also washed with water in an inert gas atmosphere andthen dried.

As for the rest, it is pointed out that the technical teaching of U.S.Pat. No. 2,895,966 is specifically directed to monoglyceride diacetates.This is particularly apparent from the paragraph linking columns 1 and2. Although it is stated by way of limitation that complex mixtures ofsubstances containing certain quantities of glycerides with only oneaceto group are normally present, it is directly and clearly disclosedthat monoglyceride diacetates in these mixtures are the critical andquantitatively dominant species for the effect to be obtained and forsolving the stated problem.

DESCRIPTION OF THE INVENTION

The problem addressed by the present invention was to provide animproved process for the production of plasticizers forhalogen-containing plastics of the epoxidized glyceride acetate type.Another problem addressed by the present invention was to provideactive-substance mixtures of epoxidized glyceride acetates not disclosedin the prior art which would be particularly suitable as plasticizingsubstances for PVC by virtue of their specific composition.

In a first embodiment, the present invention relates to a process forthe production of epoxidized glyceride acetates in which epoxyfatty acidesters are transesterified with triacetin.

Epoxidized Glyceride Acetates

In the process according to the invention, epoxyfatty acid esters arereacted with triacetin—a reaction which may be chemically interpreted astransesterification. The product present after this reaction need notnecessarily be homogeneous in the sense of a single molecular structure.On the contrary, this product is generally a more or less complexmixture of different chemical individuals. Nevertheless, such a mixtureis also referred to as “epoxidized glyceride acetate” in the presentspecification on pragmatic grounds. Depending on the desired reactionratio of the two reactants of the transesterification (see below),epoxidized monoglyceride diacetates or epoxidized diglyceridemonoacetates may represent quantitatively the dominant species of theproduct mixture.

Epoxyfatty Acid Esters

In the context of the present invention, epoxyfatty acid esters areunderstood to be:

-   a) Monoesters of fatty acids and monohydric alcohols with the    formula R¹—OH, where R¹ is a C₁₋₁₈ alkyl group which may be    saturated or unsaturated, linear or branched, aliphatic or    cycloaliphatic, with the proviso that the fatty acid part derives    from a C₈₋₂₄ fatty acid which contains at least one C═C double bond    per molecule and with the further proviso that at least one C═C    double bond per fatty acid unit is present in epoxidized form.-   b) Triesters of fatty acids and glycerol, with the proviso that the    fatty acid components derive from C₃₋₂₄ fatty acids, with the    proviso that at least 30% of the fatty acid units of the triesters    contain at least one C═C double bond and with the additional proviso    that at least one C═C double bond per molecule of triester is    present in epoxidized form.

The term “fatty acid” is familiar to the expert and is defined, forexample, in the standard work Römpps Chemie-Lexikon (cf. 7th Edition,Stuttgart 1973, pages 1107–1110).

The compounds b) are triglycerides based on the fatty acids mentionedand glycerol. The glycerides used may be synthetically producedcompounds or even fats and oils of natural origin (for a definition of“fats and oils”, see for example Römpps Chemie-Lexikon, cf. 7th Edition,Stuttgart 1973, pages 1101–1106).

Preferably at least 50% and more particularly at least 80% of the fattyacid units of the triesters b) contain at least one C═C double bond.

The proviso that at least one C═C double bond per molecule of triesterb) must be present in epoxidized form logically applies only to thosemolecules of the triester in which at least one C═C double bond ispresent because, although a triester b) by definition contains a certainproportion of fatty acid units with at least one C═C double bond,particularly where it derives from fats and oils of natural origin,molecules whose fatty acid units are all saturated may also be presentin the triester on account of the statistical distribution.

Triacetin

Triacetin is characterized by the following structure:

Triacetin is a commercially available product of which the productionhas long been known. For example, DE-A-30 04 660 describes a process forthe production of triacetin by reaction of glycerol with acetic acid andacetic anhydride.Transesterification of Epoxyfatty Acid Esters With Triacetin

The process according to the invention represents a transesterificationreaction. In this reaction, the oxirane rings (=epoxide groups) of theepoxyfatty acid esters remain intact.

The process according to the invention is preferably carried out in thepresence of a transesterification catalyst. Transesterificationcatalysts are known to the expert. They are preferably basic compounds,such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodiummethylate, sodium ethylate, and also tin(IV) compounds such as, forexample, dibutyl tin dilaurate. The quantities of catalyst used arepreferably between 0.01 and 1.0% by weight, based on the total quantityof epoxyfatty acid esters and triacetin used, and more particularlybetween 0.05 and 0.2% by weight.

The process according to the invention is preferably carried out atreaction temperatures in the range from 120 to 240° C. and moreparticularly at reaction temperatures in the range from 150 to 230° C.

The reaction times in the process according to the invention arepreferably 1 to 6 hours and more particularly 3 to 5 hours.

The molar ratios of epoxyfatty acid esters and triacetin in the processaccording to the invention are preferably adjusted to values of 1:2 to2:1.

The epoxyfatty acid esters used in the process according to theinvention are, in particular,

-   -   epoxidized esters of fatty acids and monohydric alcohols of the        type a) defined in more detail above, the alcohol units of these        esters being selected from the group consisting of methanol,        ethanol, propanol, butanol and 2-ethylhexanol;    -   soybean oil epoxide, linseed oil epoxide, sunflower oil epoxide,        rapeseed oil epoxide, tallow epoxide.

The present invention also relates to epoxidized glyceride acetatesobtainable by transesterification of epoxyfatty acid esters withtriacetin in such a molar ratio that diglyceride monoacetates arequantitatively the dominant species in the product mixture. To this end,the molar ratios of epoxyfatty acid esters to triacetin are adjusted inthe transesterification reaction to values of, in particular, 1.1:1 to2:1.

The present invention also relates to the use of epoxidized glycerideacetates, which are obtainable by transesterification of epoxyfatty acidesters with triacetin in such a molar ratio that diglyceridemonoacetates are quantitatively the dominant species in the productmixture, as plasticizers for halogen-containing organic plastics, moreparticularly PVC.

EXAMPLES

Substances used Name Explanation Vinnolit ® H 70 DF PVC (AdventInternational) Irgastab ® BZ 561 Ba/Zn stabilizer (Ciba-Geigy) Edenol ®D 81 Epoxidized soybean oil (Cognis/DE) Stabiol ® CZ 222 Ca/Znstabilizer (Cognis/DE) Loxiol ® G 10 Lubricant (Cognis/DE) Loxiol ® G 20Lubricant (Cognis/DE) Dioctyl phthalate Plasticizer (Degussa-Hüls/DE)Dioctyl adipate Plasticizer (Degussa-Hüls/DE)

Production Examples Example 1

Transesterification of Oleic Acid Methyl Ester Epoxide With Triacetin

145 g triacetin were transesterified with 205 g oleic acid methyl esterepoxide (epoxide content 4.9%) at 150° C. in the presence of 1.8 gsodium methylate as catalyst. The reaction time was 3 hours. Ca. 30 gacetic acid methyl ester were distilled off as secondary product. 320 gglycerol monoepoxyoleate diacetate were obtained. This product had thefollowing characteristics:

acid value (AV): 0.97 saponification value (SV): 390 epoxide content:3.1%

If desired, the color of the product may be improved by bleaching withca. 2 g hydrogen peroxide (30%).

Example 2

Transesterification of Epoxidized Soybean Oil With Triacetin

340 g epoxidized soybean oil (Edenol D 81) were transesterified with 161g triacetin at 220° C. in the presence of 0.25 g sodium hydroxide ascatalyst. The reaction time was 4 hours. To improve its color, theproduct was bleached with ca. 2 g hydrogen peroxide (30%). Ca. 500 gglycerol monoepoxyoleate diacetate were obtained. This product had thefollowing characteristics:

AV: 0.86 Lovibond color 1″: yellow: 5.6, red: 1.0 epoxide content: 4.1%

Example 3

Transesterification of Epoxidized Soybean Oil With Triacetin

340 g epoxidized soybean oil (Edenol D 81) were transesterified with 161g triacetin at 220° C. in the presence of 0.25 g dibutyl tin dilaurateas catalyst. The reaction time was 3 hours. To improve its color, theproduct was bleached with ca. 1 g hydrogen peroxide (30%). Ca. 500 gglycerol monoepoxyoleate diacetate were obtained. This product had thefollowing characteristics:

AV: 1.2 Lovibond color 1″: yellow: 6.2, red: 1.0 epoxide content: 4.0%

Application Examples

Formulations F1 to F8 based on various plasticizers were produced forperformance testing. The composition of these formulations is shown inthe following Table.

The quantities in which the individual components are used are expressedin “phr” which stands for parts per hundred resin and indicates how manyparts by weight of the particular substance are present in the PVC afteraddition of the composition, based on 100 parts by weight PVC.Accordingly, the formulations all contain 100 parts PVC (Vinnolit H 70DF).

It is specifically pointed out that, in the case of F1 to F8, it isimportant to distinguish between the overall formulations, which areused for performance testing and which contain all the componentsmentioned, and the actual additive compositions which contain all thecomponents mentioned except for the PVC.

F1 F2 F3 Vinnolit H 70 DF 100 100 100 Irgastab BZ 561 1.5 1.5 1.5Dioctyl phthalate 100 0 0 Dioctyl adipate 0 100 0 Compound of Example 10 0 100 F4 F5 F6 Vinnolit H 70 DF 100 100 100 Edenol D 81 8 8 8 StabiolCZ 2222 1 1 1 Loxiol G 10 2.5 2.5 2.5 Loxiol G 20 0.2 0.2 0.2 Dioctylphthalate 30 0 0 Compound of Example 2 0 30 0 Compound of Example 3 0 030 F7 F8 Vinnolit H 70 DF 100 100 Edenol D 81 8 8 Stabiol CZ 222 1 1Loxiol G 10 2.5 2.5 Loxiol G 20 0.2 0.2 Dioctyl adipate 50 0 Compound of0 50 Example 3

Strips were produced on the basis of formulations R1 to R8 and weretested for static thermal stability at 180° C. The strips were producedby homogenizing and plasticizing the formulations mentioned for 5 mins.at 170° C. on laboratory rolls. Test specimens measuring 17×17 mm werecut out from the ca. 0.5 mm thick strips thus produced.

The following measurements were carried out with the test formulations:

-   -   Stability test at elevated temperature: strips were produced        from the formulations and tested for static thermal stability at        180° C. The strips were produced by homogenizing and        plasticizing the components of the formulations mentioned for 5        mins. at 170° C. on laboratory rolls. Test specimens measuring        17×17 mm were cut out from the ca. 0.5 mm thick strips thus        produced. The test specimens arranged on glass plates were        placed on rotating shelves in a heating cabinet at 180° C. and        removed at 15-minute intervals until all the test specimens were        “burnt” (i.e. had turned black in color).    -   Color measurement of strips: in addition, the L*, a*, b* method        known to the expert (cf. DIN 6174) was applied to the strips for        further characterization. The initial color of the strip        (yellowness value b*) was determined. A commercially available        instrument (“Micro Color”, manufacturer: Dr. B. Lange) was used        for the measurements.    -   Shore A hardness: the Shore A hardness of the strips as known to        the relevant expert was determined to DIN 52505 using a        commercially available Shore hardness tester (manufacturer:        Zwick).    -   Light transmission: the light transmission of 4 mm thick pressed        plates based on the formulations mentioned was determined. The        pressed plates were produced from the strips. The strips were        pressed between two pressing plates of a laboratory press        (Collin) with spacers in between to form plates with the        thickness mentioned. In the tests carried out, 8 strips each 0.5        mm thick were pressed at 170° C./250 bar to form a 4 mm thick        pressed plate.    -   Compatibility: by compatibility is meant the compatibility of        the additive compositions with the plastic (PVC). The        compatibility of the strips was determined after storage at room        temperature. The strips were tested for compatibility by visual        examination. The surface of the strip was evaluated for signs of        exudation. In this method, serious exudation is an indicator of        serious incompatibility; the absence of exudation is an        indicator of very good compatibility.

The results obtained with the test specimens are set out in thefollowing Table. C1 is a test specimen based on additive composition R1,C2 is a test specimen based on additive composition F2, etc.

C1 C2 C3 Thermal stability (180° C.) 75 mins. 60 mins. >270 mins. ShoreA hardness 61   58   65   Transparency (light transmission in %, 83  76   83   4 mm pressed plate) Compatibility after production Very good,no Very good, no Very good, no exudation, exudation exudationCompatibility after 6 months (storage Very good, no Very good, no Verygood, no at room temperature) exudation exudation exudationCompatibility after 12 months (storage Very good, no Very good, no Verygood, no at room temperature) exudation exudation, exudation C4 C5 C6Thermal stability (180° C.) 90 mins. 210 mins. 210 mins. Shore Ahardness 90   93   93   Initial color of the strip (yellowness 4.7 6.35.8 value b*) Compatibility after production Very good, no Very good, noVery good, no exudation, exudation exudation Compatibility after 18months (storage Very good, no Very good, no Very good, no at roomtemperature) exudation exudation exudation C7 C8 Thermal stability (180°C.) 75 mins. 240 mins. Shore A hardness 73   80   Initial color of thestrip (yellowness 2.6 4.3 value b*) Compatibility after production Verygood, no Very good, no exudation exudation Compatibility after 10 weeks(storage Very good, no Very good, no at room temperature) exudationexudation,

1. A process for the production of an epoxidized glyceride acetate which comprises reacting an epoxy fatty acid ester and triacetin.
 2. The process of claim 1 wherein the epoxy fatty acid ester is a triester of a fatty acid and glycerol wherein the fatty acid components of the triester are derived from C₃₋₂₄, fatty acids, with the proviso that at least 80% oft. fatty add units of the triesters contain at least one C═C double band and with the additional proviso that at least one C═C double bond per molecule of triester is present in epoxidized form.
 3. The process of claim 1 wherein the process is carried oat in the presence of a transesterification catalyst.
 4. The process of claim 3 wherein the catalyst is used in a quantity of from 0.01 to 1.0% by weight, based on the total quantity of epoxy fatty acid ester used and triacetin.
 5. The process of claim 1 wherein the process is carried out at a temperature of from 120 to 240° C.
 6. The process of claim 1 wherein the process is carried out in a time period of from 1 to 6 hours.
 7. The process of claim 1 wherein the mole ratio of epoxy fatty acid ester to triacetin is from 1:2 to 2:1.
 8. A process for the production of a product comprising a major amount of an epoxidized diglyceride acetate which comprises reacting an epoxy fatty acid ester and triacetin wherein the molar ratios of epoxy fatty acid esters to triacetin is from 1:2 to 2:1.
 9. A method of plasticizing a halogen-containing plastics comprising adding to a halogen-containing plastic a plasticizing-effective amount of a compound of claim
 8. 